Case neck clearance question

[thespecialist]

Alright, so I recently had to scrap some of my 260 cases because the primer pockets finally went south. I'll be honest and admit that I'm a bit of a tightwad and am not going to spend $1 per case for Lapua when I get 8-10 pretty damn warm loadings out of RP brass.

While I was tossing those in the scrap bin, I couldn't help but notice all of the Winchester 308 brass I have. I ran a couple through my FL bushing sizer and brought the neck down to .288 since I didn't have a .290 bushing. This gave me .0045 neck tension (too much, I know) and a loaded OD .003 bigger than with my RP brass. That made sense to me because the case necks on the 308 brass are .015" where my RP 260 brass is .0135.

With my RP brass, I have a loaded neck diameter of .290" and a fired neck diameter of .297" so my chamber has .006" clearance with those cases. Since my 308 cases are .003" larger in the neck, that cuts the clearance to only .003" for the neck to expand on firing.

Is .003" enough to not cause any issues?

 

[korykhunter]

I have less than .002 in my 22-6mmIMP with no issues.

 

[MitchAlsup]

With clean ammo you can get by with 0.001 neck clearance radially but you still want 0.005" longitudinally to the end of the throat.
When any dirt is envolved you are going to want 0.003 radially. Most factory chambers have 0.008 through 0.012.